Electron tube cooling system



June 30, 1936. N. E. LINDENBLAD ELECTRON TUBE COOLING SYSTEM 2 Sheets-Sheet l Filed March l5, 1955 INVENTQR N\L5 E. UNDENBLAD ATTORNEY June 30, 1936. N. E. I INDENBLAD ELECTRON TUBE COOLING SYSTEM Filed March 15, 1935 2 Sheets-Sheet 2 INVENTOR NILS E. LINDENBLAD Y @MCM ATTORNEY Patented June 30, `1936 UNITED STATES PATENT OFFICE TUBE COOLING SYSTEM Delaware Application March 15, 1935, Serial No. 11,217

' 5 Claims. (Ul. Z50-27.5)

My invention relates to cooling systems for thermionic discharge devices and is particularly concerned with air cooling means for high powdered radio tubes.

High power radio tubes are usually cooled by water circulated thru water jackets placed about the exposed metal portions, such as the cylindrical anodes of the transmitter type of tube. Water cooling has some disadvantages, such as the diiliculty and expense of making the cooling system water tight. Leaks in the water system dampen the exterior surfaces of the tube and may create objectionable leakage paths for the high potentials applied to the tube. The water feed pipes to the anodes, which are usually at high potentials above ground, provide comparatively low resistance paths to the circuit between the anodes and ground. Further, the usual Water cooling jackets surround only a portion of the anode and do not cool directly the glass of the tube or the glass-to-metal seals between the anode and the glass envelope. It is particularly important that these seals be cooled since tube failures may result at high temperatures from unequal expansion of the glass and metal at the seal.

An object of my invention is to provide an lmproved cooling system for thermionic discharge devices.

A further object of my invention is to provide for radio tubes an air cooling system that gives more complete and uniform dissipation of heat.

A still further and more specic object of my invention is to provide a cooling arrangement which cools not only the glass and metal portions of the tube, but also the glass-to-metal seals between the glass and metal parts.

In accordance with my invention I provide the exposed metal portions of the tube, such as the anode and grid terminals, with radiating members and. circulate air, preferably under pressure, over the radiating members. In one embodiment of my invention the radiating member forms an integral part of an electrical tuning circuit for the tube. l

A more complete understanding of my invention will be had by referring to the accompanying drawings in which Figure 1 shows one form of tube embodying my invention; Figure 2 shows a cross section along line 2 2 of Figure 1; Figure 3 is a bottom view of the tube and cooling means shown in Figure l; Figure 4 shows my invention applied to a second form of tube; Figure 5 shows my invention applied to an ultrashort wave oscillator; Figure 6 is a sectional view along the line 6-6 of Figure 5; Figure '1 shows a slightly modied form of my cooling radiator applied to a standard tube; and Figure 8 is a section along the line 8 8 of Figure '1. Throughout the drawings, like parts are indi- 5 cated by similar reference characters.

Figure 1 shows a conventional type of high power tube having an envelope consisting of a 4glass portion I and a cup-shaped metal anode 2 sealed at its edge to the glass portion of the 10 envelope. The upper end of the envelope carries cathode leads 3, and the side wall of the glass portion is protruded, as at I, to form a base for a grid terminal member 5 of any standard construction and hermetically sealed into the protuberance I. Integral with the terminal 5 is an outwardly extending pin 6 to which is usually connected the external grid lead.

In applying my invention to this form of tube the anode and the grid terminal, and also the seals, if desired, are air cooled. For cooling the grid terminal the grid lead is replaced by a hollow cup-shaped sleeve 'l with a conical exterior surface iitted over the pin and secured to it either by a ground t or by the sweating in of some heat conducting adhesive. such as lead, as shown at 8. An outer radiating member 9 with a turned out conical recess conjugate with the external surface of the sleeve member is secured to the outer surface of the sleeve member 1 by a bolt I0. Extending longitudinally thru the radiating member 9 is a series of circularly arranged holes or cooling ducts Il terminating at their inner ends adjacent the grid terminal member 5. For directing the cooling air to the grid terminal seal I prefer to secure to and around the radiating member a cylindrical skirt-shaped shield I2 which may be held in position as by a frietional at or by welding. The 1an or inner 40 end of the skirt is'flared as shown at i3 to permit the ready exhaust of air from ducts II. To the radiating member is fastened a Suitable grid lead connector i4, and to the outer end of the radiating member is secured a short section of insulating pipe I5, formed of glass or bakelite for example, which in turn is connected at one end to an air supply duct I6, which in turn may be formed of insulating material, such as rubber hosing. Air duct I6 is connected to the outlet 50 Vof any suitable air pump or fan for delivering air under any desired pressure to the inlet ends of duct passages Il. The air in passing thru ducts Il serves to cool the radiating member 9, which in turn cools the contacting metallic parts of the pin and terminal member. The air upon leaving the inner ends of the duct passages Il flows against the glass walls of the envelope and protuberance 4 and against the glass-to-metal'.'

seal between the terminal member and protuberance. It will be noted that by this-,construction the terminal member and its pin are cooled by the same stream of air which cools the glass and its seal to the metal, thus minimizing the diiference of temperature between the adjacent glass and metal parts. 'By maintaining the temperatures of these parts nearly equal, unequal expansions or contractions between the glass andmetal are reduced, thusaminimizing fractures the seal.

The anode 2 of the tube is provided with radial cooling ns I1 which may be iormed integral with the anode or fabricated upon a sleeve ground titY internally to make intimate contact with the outer surface of the anode. As best shown in Figure 3 air under pressure is introduced tangentially thru an air supply pipe or duct Il to the spaces between the radial ns and exhausted thru an opening at I9. Air pipe or channel I 5 -may be formed of insulating material such as The anode 2 is provided with two oppositely extending glass sleeve portions I, and in the upper end of the upper glass sleeve is sealed cathode lead wires 3. Surrounding glass portions I, of the tube are hollow annular ring members 30, which in vertical cross section are rectangular in outline as shown. The rings are positioned concentrically with the cylindrical envelopes I, and are spaced therefrom along al1 radial lines thru the envelope. In the inner wall of each ring member intermediate its ends is a circumferential opening or recess 3|.y At one side and exteriorly thereof is constructed` an inlet air duct nipple 32 which serves to support the ring members upon the supporting panel 33. The tube body may be supported within the ring members and centrally ilxed therein by end plates 34. To the ends of the nipples 32, are suitably secured arsupply pipes 35, which are connected to anair supply source thru the pipe 36. Air under pressure entering at 36 divides into passages 35, and iiows thru nipple members 32. From the interior of the annular ring members, the air is directed forcibly against the walls of the envelope and deilected upwardly and downwardly towards the ends of the annular members. As is evident from the drawings, one-half of the exhausted air iiows against the metal parts of the anode 2, the other half circulating about the end electrode terminals.

In Figures 5 and 6 I illustrate how my improved cooling system may be extended to form part of the oscillatory system of a short-wave oscillator or amplifier. Power tubes I, with their anodes 2 (Figure 6) are so related as to constitute a conventional push-pull ampliiier or oscillator for ultra-short waves which may be operated for example on the Barkhausen-Kurz principle. In the construction illustrated in Figure 5 the heat radiating members comprise the tuning' Lecher wires for the stage. in Figure 1 a sleeve 4l is itted over the outer surface of the cylindrical anodes. On the sleeve member is formed lcircular cooling fins 4I4 which extend circumferentially of the sleeve. Radial ns 4I are cast with extensions or radiating members 42 and 41, 5 which in general are narrower than the diameter of the circular portions thereof and are extended radially outwardin opposite directions a distance substantially greater than the diameter of ns 4|. The edges of the uns 4I, 42 and 41 are covered by plates 43 which extend the full length of the flns, thus forming a plurality of parallel rectangular air passages. At one end of each of' the ilns 42 is troduced air under pressure whichv passes thru e ducts around the anode andout the opposite ends oLthe air passages. Radiating members 42 and 41, when formed oi' any good Aheat conducting material such as metal, may be employed as long lines or Lecher wires to electrically tune the tubes. By means of sliding bars 20 44, in combination with condenser 45, the tubes 'may be adjusted to resonate at any desired opg or cup-shaped anode 2 is secured a hollow conical shaped cup member 5l, which may be either ground iitted to the anode or sweated thereon with solder 5| as described above in connection with member 1 of Figure 1. Fitted over the conical exterior surface of the sleeve 5l is secured cup-shaped'member 52, by abolt 53. Formed integral with the cup-shaped member 52 to extend from one side thereof is a bar or rod 54. Member 54 may take any desired cross sectional form which by way of example is shown as circular in Figures 'T and-8. Extending longitudinally thru the bar is a series of circular-ly arranged air ducts 55, which at their inner ends terminate adjacent the cup-shaped member 52. 551s a hollow cylindrlcally shaped skirt member positioned concentrically about the bar 54, 'and to form an annular space 53 is spaced from 54 by means of perforated end member 51. Air under pressure is introduced at the right hand end of the bar and skirt members 'from an insulating hose connection 58. Cup-shaped members 5l and 52, which are formed of any good heat conducting material, transmit most of the heat from the anode along the bar member 54 where it is dissipated in the air stream thru passages 55 and the annular space 53.` The air from the exhaust end of the ducts 55 and annular passage 53 is directed against the glass of the envelope I,

. against the glass-to-metal seal at the anode and against the grid terminal 5. With this arrangement of`parts'the entire transmitter tube including its anode and terminal members are eiectively cooled from a single and inexpensive source ofcooling air.

The characteristic feature thruout the vari- Vous forms of my invention lies in the fact that the anodes, electrode terminals and glass-tometal seals are cooled uniformly by a single source of cooling media and in the fact that the conduits for the cooling media provide high resistance paths between the parts oi.' the tube and ground. Y

Having described my invention, I desire to be limited only'by the prior art and by the appending claims.

v What I claim as new is:

1. A thermionic discharge device comprising an envelope for enclosing cooperating electrodes,

terminals for said electrodes extending exteriorly of said envelope and sealed in insulating material in the wall thereof, an apertured heat radiating member of good heat conducting material secured to one of said terminals, means for introducing air under pressure at one end of the apertures, the other end of the apertures being positioned to direct the air against the envelope adjacent the seal.

2. An electron discharge device comprising a gas tight glass envelope for enclosing an electrode, an electrical connection for said electrode thru the Wall of said envelope comprising a metallic terminal member of considerable bulk sealed in the glass, a heat radiator on said member, means for cooling the glass-to-metal seal and said member comprising means for directing a stream of cooling Iluid through said heat radiator and against the terminal member and the glass adjacent thereto.

3. An electron discharge device comprising an impervious envelope with a vitreous wall, an electrode terminal member of metal sealed in said wall of the envelope and extending exteriorly thereof, a heat radiating member secured to said member and in direct metallic contact therewith over a substantial portion of the surface of the terminal member, said radiating member being provided with air ducts, inlet means for introducing air under pressure to one end of said ducts, the other ends of the ducts said anode, circular cooling flns attached to and in good heat conducting relationn with said sleeve, said fins having relatively narrow parallel portions extending radially beyond the periphery of said circular cooling iins,closure means over the edges of said fins and their extended portions, and means for introducing air at the outer ends of the extended portions oi said uns. l5

5. A thermionic discharge device comprising a cylindrical anode closed at one end, a tubular glass envelope hermetically sealed at one end tc the open end of said anode, an electrode terminal sealed into the glass wall of said envelope, the

terminal being spaced from the anode-to-glass seal, a cup-shaped member of good heat conducting material fitted over and in intimate contact with the outer wall of said anode, said member having an outwardly extending bar with longitudinal ducts, said ducts terminating at one end adjacent the cup-shaped member, a. shield ci substantially the same length as said bar and greater diameter placed concentrically about said bar, and means for introducing air at the outer end of said bar and shield.

NILS E. LINDENBLAD. 

